National Weather Radio (NWR), a division of the National Oceanic and Atmospheric Administration (NOAA) broadcasts continuous weather related information in the VHF frequency band between 162.400 and 162.550 MHZ. This information is repeated every 4 to 6 minutes and updated every one to six hours throughout the day. When sever weather (or any other event that poses a threat to life and/or property) occurs, the information is updated more frequently.
In the event of sever weather, a unique message is broadcast—one that is preceded by a warning alert tone (WAT). The WAT has a frequency of 1050 Hz and can be broadcast for 8 to 10 seconds. This tone allows a weather radio to detect the warning, respond by sounding an alarm, and unmuting its audio so that a user can listen to the sever weather alert. In addition to the WAT, NWR has implemented an advanced alerting system known as “Specific Area Message Encoding” (SAME). This system adds a digital message, consisting of the warning and its target location, to the weather alert so that specially equipped radio receivers can provide a more location-specific weather alert. One weather radio that takes advantage of SAME is the “Radio Shack 7-Channel Weatheradio with NWR-SAME Severe-Weather Alert.” This radio can receive and process the digital message provided by NWR, but requires the user to input specific county codes into the device through a keypad. This radio can be set to sound an alarm when the National Weather Service issues a weather warning, watch, or statement that corresponds with the user-selected county codes. The radio can also be configured to give a visual indication of the type of weather alert being broadcast instead of an audible alarm.